Pitot-static tube



1934. J..D. PEACE, JR 1,971,534

PITOT STATIC TUBE Filed Aug. 11, 1932 IN V EN TOR. JO/l/V D. PEACE, Jr.

ymwma A TTORNEX Patented Aug. 28, 1934 Bendix Aviation Corporation,South Bend, 1nd,, a poration of Delaware 1 Application August '11, 1932,Serial No. 628,429

I teams. (01. is ie'nf The present invention -relates-toPitot-statictubes of the type adapted for use on aircraft to determine the air speedof the latter and more particularly to means for heating said tubes.

One of the objects of the invention is to provide a novel Pitot-statictube embodying avconstruction of simple design which is easy to assembleand disassemble, thereby facilitating rem placement-of parts, and a.construction which renders the tube particularly suitable and efficientfor use in obtaining the air speed of anair-- craft. v

Another object is to provide a Pitot-static tube embodying novel meansfor heating the same whereby the forming of ice or the packing of snowat ,the entrance of the tube or within the chamber which communicateswith the moving air may be obviated so that proper function- 2 ing ofthe tube may be assured when fiying'during cold, weather or in inclementweather.

Another-object is to provide in a Pitot static tube having two chambers,one of which is adapted to receive the impact of an air stream fortransmitting the velocity pressure and. the

other of which is open to the surrounding at-- mospherebut unaffected bythe air stream for transmitting the static pressures, a heating coil forone of said chambers, and novel means whereby said coil may beautomatically connected in an electric circuit upon the placing andsecuring of said coil in said chamber, therebyeliminating the necessityof making manual connections of wires to terminals or binding posts. v e

A further object of the invention is to provide a novel heating coilfor-Pitot-static tubes whereby said coil may be readily removed from thetube and replaced by another without re-' quiring disconnecting andconnecting of wires, and which is automatically placed in an electriccircuit by merely positioning the'coil within the chamber of the tubewith which it is associated. The above and otherobjects and'advantagesand novel features of the construction and combination of .parts ofthedevice embodying the present invention will appear more fullyhereinafter from a consideration of ithe detailed description whichfollows, when taken in conone embodiment of the invention isillustrated. It is to beexpressly understoodhowever, that the drawing isfor the purpose of illustration and description only and is not designedas a definition of the limits of the invention. reference fner ofsupporting the same for operation;

nection with the accompanying drawing whereinbeing had for this purposeto the appended claims. 1

In the drawing wherein like reference characters refer to like partsthroughout the several views,

Fig. 1 is a longitudinal section of one form of novel Pitot-static tubeembodying the present invention; I

Fig. 2 is a side'view thereof showing the'man- Fig. 3 is an end view asviewed from the left of Fig. 2; and

Fig. 4 is a detail view showing the manner in which the novel heatingcoil of the tube is constructed and assembled.

The Pitot-static tube embodying the present invention is of the typedisclosed in a copending application of Charles H. Colvin, Serial No.261,466 filed March 14, 1928, and comprises, in the form shown herein,three sections 5, 6 and 7. The section'5 is in the form of a metal tubeor casing having one end thereof curved inwardly as indicated at 8 andthe other end threaded internally as indicated'at 9' for securing thetube to the middle section 6. The other outer sec- 0 tion 7 has one endthereof closed in any suitable manner as, for example, by means ofastreamlined cap 10 and is also secured to the middle section 6, as bymeans of a pressed fit. The section 5 is provided with an opening 11 andconstitutes the velocity pressure end of the Pitotstatic tube fortransmitting pressures due to velocity head, and the other section 7 isprovided with a plurality of apertures 12 in the walls thereof and isutilized for transmitting pressures due to static or pressure head.coinciding with the opening 11 at the end of the tube 5 and extendingwithin thelatter is a tube 13 having its inner end closedby a plug 14 inwhich are provided openings 15 and 16 and to which is secured or formedintegral therewith a bafiie plate 17, the latter serving to preventforeign materials from entering the tube and being passed to theair-speed indicators.

Supporting member 6 is provided with a pair of passages 18 and 19 whichconnectwith the sections 5 and 7 respectively. A'pair of tubes 20 and 21extend transversely of and into the supporting member 6 and connect withthe passages 18 and 19, respectively, by means of cut away portions 22and 23 provided at their ends for transmitting the pressures producedwithin the tubes 5 and '7 to a remote point, as for example to aninstrument panel on an aircraft Where they may be connected to an airspeed is mounted is flying at high altitudes where very low temperaturesare prevalent, or when flying in inclement weather, ice tends to form orsnow tends to pack at the opening 11 of the tube, thereby clogging saidopening or completely closing it andrendering the tube inoperative. Itis, therefore, desirable to prevent such ice formations, and for thispurpose means are provided whereby the velocity tube 5 may be heated,thus preventing ice and snow from adhering to the tube. In the formshown, such means comprise a heating coil 24 which may be connected inan electrical circuit by means of a singlewire-ground-return systemincluding a sourceof electric current (not shown) for heating said coil.I

It is also desirable that the coil 24 be readily and easily insertedinto and/or removed from the tube 5, thereby facilitating thereplacement thereof. To this end a novel construction is employedembodying novel means whereby the coil is automatically interposed intothe electrical circuit upon the placing thereof within the tube 5 andupon securing of the latter to the supportingmember 6. This may beaccomplished as shown in the detailed view in Fig. 4. In order to effectthe automatic interposition of the coil into the circuit, said coil isprovided at either end thereof with flanged collars 25 and 26,respectively, to which are adapted to be soldered ends 2'7 and 28 of theheating coil 24. and the collars are then placed over the ends of thecoil to provide contact surfaces, one of which (collar 25) contacts withthe interior surface of the tube 5, as shown in Fig. 1, and the other ofwhich is adapted to contact with a resilient conducting ring 29 imbeddedin an insulating ring 30, said ring 29 having soldered thereto end 31 ofa suitable insulated cable 32. The-cable may be connected to a source ofcurrent (not shown) such as a battery, for example, having one terminalthereof grounded. The return circuit of the coil is then providedthrough the ground formed by any suitable metal structure with which thetube is associated so that the collar 25, by virtue of its contact withthe metal tube 5, constitutes the grounded side of the coil 24.. Theconductor 32 is led out of the tube through a recess 33 provided in theupper portion of the supporting section 6 and through a tube 34 similarto the tubes 20 and 21, extending transversely of. and partly into saidmember 6.

The three tubes 20,21 and 34 are held together by means of suitableclamps 35 and 36 and are bent in such a manner that the Pitot-statictube projects from its support (not shown) to which the'three tubes maybe clamped, as by means of brackets 3'7 and 38.

It will be apparent from the foregoing that when it is desired toremovethe heating coil 24 for inspection or replacement thereof in case of itsbeing burned out, all that is necessary to do is to unscrew the tube 5from the supporting memberjfi' and remove the coil from said tube. As"soon as the tube 5 is unscrewed from the section ',6,the heating coil,by virtue of the disengagement of the collar 26 from the ring 29, isimmediately disconnected from its electrical circuit withoutnecessitating the disconnection of any wires. .A new coil may then beplaced within the tube 5 so that the collar 25 at one thereof contactswith the inner wall of said tube and the latter may then be secured tothe supporting member 6 by means of the threads 9, whereupon the collar26 at the other end of the coil presses firmly against the resilientring 29 which is permanently connected to the insulated conductor 32.

There is thus provided a Pitot-static tube embodying a novel structureof a heating unit whereby the latter may be easily and quickly assembledand/or replaced without requiring connecting and disconnecting of wiresfrom terminals and whereby the coil is automatically interposed in theelectrical circuit which is adapted to energize it, by simply placingthe coil within the nosepiece of the tube and securing said nosepiece tothe tube.

- Although only one embodiment of the invention has been illustrated anddescribed, various changes and modifications in the form and relativearrangement of parts, which will now appear to those skilled in the art,may be made without departing from the scope of the invention. Referenceis, therefore, to be had to the appended claims for a definition of thelimits of the invention.

What is claimed is:

1. In a Pitot-static tube unit having a metal tube section, one end ofwhich is open to receive the impact of an air stream, a second tubesection, the sides of which have apertures connecting it to thesurrounding atmosphere, a member interposed between said tube sectionsfor supporting the same, said member having two passages, one of whichconnects to the first tube section and the other of which connects tothe second tube section, the combination of an electrical heating coilin said first tube section and having metal collars at its ends to whichthe opposite ends of the winding of the coil are electrically connected.thereby providing contact surfaces for said coil, one of said surfacesbeing in contact with the inner surface of said first tube section, andmeans including a lead wire adapted to contact with the other surface ofthe coil when said tube section is secured to the supporting member,said lastmentioned means being insulated from said tube section. I

2. In a Pitot-static tube unit comprising a removable metal tube sectionhaving one end open to receive the impact of an air stream, a

second tube section which is closed but which is provided with one ormore apertures for establishing communication with the surroundingatmosphere, and means for connecting said tube sections to adifierential pressure-responsive de= vice, the combination of anelectrical heating coil in said first tube section and having metalcollars at its ends to which the opposite ends of the coil areelectrically connected, thereby providing electrical contact surfacesfor said coil, one of said surfaces being in contact with the innersurface of said first tube section when the latter is placed inposition, and means including a lead wire adapted to contact with theother surface of the coil when the latter is held in the unit by thefirst tube section, said last-mentioned means be-= ing insulated fromsaid tube section.

3. In a Pitot-static tube comprising a removable metal tube sectionhaving one end open to receive the impact of an air stream, a secondtube section which is closed but which is provided with one or moreapertures for establishing communication with the surroundingatmosphere, an annular member interposed between said tube sections andto which the latter are secured, and

means for connecting said tube sections to a differentialpressure-responsive device, the combination of an electrical heatingcoil in said first tube section and having metal collars at its ends towhich the opposite ends of the coil are electrically connected, therebyproviding electrical contact surfaces for said coil, one of saidsurfaces being in contact with the inner surface of said first tubesection when the latter is secured to the intermediate member, and meansincluding a lead wire adapted to contact with the other surface of thecoil, said last-mentioned means being insulated from said tube section.

4. In a Pitot-static tube having a removable metallic tubular portionconstituting an electrical ground return, the combination of anelectrical heating coil within said metallic tubular portion, and meansfor automatically connecting said coil in an electrical circuit uponsecuring of the coil within said metallic tubular portion and to saidtube, said means comprising an insulated ring concentrically positionedwithin the metallic portion of said tube, a resilient conducting ringwithin said insulated ring, a lead wire secured to said conducting ringand providing an external connection from one end of said coil, and apair of conducting collars carried by the ends of the coil andelectrically connected to the respective ends of the winding thereof,one of said collars being adapted to bear against the resilientconducting ring upon securing of the coil within said metallic tubularportion and to said tube, and the other collar being adapted to bearagainst the inner surface'of the metallic portion of the tube forgrounding the other end of the coil.

JOHN D. PEACE, JR.

